Circadian and seasonal variability of resting frontal EEG asymmetry.

Asymmetrical frontal cortical activity at resting baseline relates to important aspects of personality and psychopathology. However, some research has failed to replicate these relationships, perhaps because of situational influences. The present research investigates two situational variables, circadian and seasonal variability. These variables affect basal cortisol levels and mood, which have also been found to relate to resting asymmetrical frontal activity. Results of two correlational studies revealed that relative right frontal activity was greatest during fall mornings. These results suggest the importance of assessing time of day (TOD) and time of year (TOY) effects on resting frontal EEG asymmetry, which could reflect circadian and seasonal influences, but also selection effects when participants are free to select among study session times.